The present invention relates to a moving image communicating system and an image restoring method an apparatus. More particularly, it concerns a motion image communicating system and an image restoring apparatus having a correcting arrangement for correcting an image disturbed by a transmission error.
Previous communication systems for transmitting compressed image data generally use an error correction code to prevent transmission error from disturbing an image. If the code cannot correct the disturbed image, a restoring method usually corrects the data.
The correction process on the restoring side is carried out by looking at pixel data of a preceding frame before replacing error data by calculated correction values. Such a method is limited to processes of fast motion images and the switching of scenes. For this reason, the Japanese Patent Application Laid-Open No. 5-227517 disclosed a method employing in-frame and between-frame correction processes before and after an expansion of compressed image data to control one of the processes depending on the degree of the error.
However, the proposed method performs the correction process in units of a block which is not effective for a radio transmission involving a random error, due to decrease of the signal-to-noise ratio and long burst error due to fading.
On the other hand, a communication apparatus for radio transmitting of image data makes use of an error correction code and interleave and resend processes to overcome random error and fading. For example, MacDonald, N., proposed a system having an error correction feature intensified with use of the three methods mentioned above in an article entitled "Transmission of Compressed Video Over Radio Link: Visual Communication and Image Processing '92." However, this system has the disadvantage that a communication apparatus on a send end involves a process delay when it has to process motion image data at any time, since it stops an encoding process temporarily while it is executing a resend process.
As described above, prior arts methods involve the problem that the motion image transmission system for transmitting continuous image signal over plurality of frames produces an in-frame and a between-frame, but cannot always be effective in the correction process for a radio link that is likely to have a burst error. The system also does not take into account the delayed process in executing a resending of the blocks whenever an error occurs.